Actually the time taken depends (mainly) on the number of vertices/polygons in the cloth and the number in the object that is being collided with. The problem is, that for dynamic cloth to look good, it really needs a lot of small polygons (because the basic polygons don't really get changed much, just moved). So If you start with a cylinder (eg for a skirt) that just consists of a load of flat 4-vertex ploygons going from top to bottom, it'll calcluate fairly quickly, but you'll end up with something that looks more like Roman armour than cloth. To make it fold around, say, a bended knee, it has to be subdivided vertically (quite a lot). More polygons = more tests for collision = more time. Cheeers, Diolma (* off to make more coffee..*)